1. Field of the Invention
The present invention relates generally to electrical connectors and the like. More specifically, the present invention relates to an electrical bonding block with a grounding lug for grounding the shielding or other ground of an electrical conductor, e.g., coaxial cable.
2. Description of the Related Art
A number of specialized electrical conductors have been developed in the past, with the various conductors serving various purposes and functions. One type of conductor commonly used for the conduction of relatively high frequency signals (e.g., television and very high frequency radio signals) is the shielded coaxial cable. Such cables essentially include a centrally located relatively thin center conductor enclosed in a relatively thick insulating material, with the insulator in turn being shielded by an electrically conductive shield to prevent interference with any electrical signal being conducted by the conductor. Such cables are commonly installed for household television systems, whether using satellite, cable, or broadcast antenna reception.
Such cable installations universally require connections at various points, such as at the entrance through the wall of the structure. Opposed externally threaded (male) connectors are universally used to connect the two ends of the exterior and interior coaxial cables at this point, with the cable ends generally including captured internally threaded connector nuts or fittings, or sometimes a slip-on attachment over the male threaded connectors. However, some means is also required for grounding the coaxial cable connection. Accordingly, various electrical bonding blocks, as they are known, have been developed, which serve as the connector for two lengths of coaxial cable and which also include some means for connecting the block to an electrical ground.
Quite typically coaxial cables are used to carry an RF signal from an antenna or external cable TV or telephony installation to a radio or television receiver or to a telephone. The center conductor usually carries the signal, and the shield is usually at circuit ground potential. Coaxial cable connectors include a tubular center pin to which the cable center conductor is attached, e.g., by soldering, and the shield is typically clamped to an external shell that encloses insulation surrounding the center pin.
While this arrangement is adequate for carrying the typical low voltage-low current RF signals received at an antenna, typically it is necessary to protect the installation from transient high voltage-high current incidents, such as lightning strikes. Without some form of protection, the transient voltages and currents may be carried by the coaxial cable, with resulting damage to television and radio receivers and other electronic equipment connected to the household wiring, and may potentially start fires by overloading and melting the coaxial cable or household wiring. Consequently, an external ground wire is clamped to the antenna mast and routed to a ground rod or other earth ground, such as metal plumbing pipes. An electrical bonding block is typically mounted to the building or other structure, and has a coaxial cable connector to connect coaxial cables in series, and a clamp to secure the external ground wire, which may be solid wire or stranded wire, and may be copper wire, aluminum wire, or the like. The shield of the coaxial cable is connected to the ground wire through the bonding block. Grounding the coax shield is often supplemented by using a lightning arrestor in the coax line between the antenna and the receiver or other electronic equipment.
Typically, such conventional electrical bonding blocks have a ground wire passage with a screw or bolt installed radially to the ground wire passage. The screw or bolt is tightened directly against the ground wire inserted in the passage, to form an electrical connection to ground. The problem with such direct engagement is that the relatively small “point” area of contact of the tip of the grounding screw with the ground wire causes the ground wire to deform at that point, and nearly always induces a “stress riser” in the wire, which weakens the wire at that point. This is particularly true where relatively soft metal (e.g., copper or aluminum) is used for the ground wire. Slight movement of the wire relative to the grounding lug will always occur over time, with such movement working the wire about the sharp engagement of the ground screw therewith and the stress riser. This eventually work hardens the ground wire, making it brittle, and weakens the ground wire sufficiently that it breaks. Even before breakage, stress corrosion often occurs in the stress riser formed in the ground wire, which increases the electrical resistance of the connection well beyond desired limits.
A few electrical grounding devices have been developed in the past that avoid the direct contact of the tip of a screw or bolt with the ground wire. An example of such a device is found in Japanese Patent Publication No. 64-2263, published on Jan. 6, 1989. This device uses a rectangular washer with downwardly folded corners, which engage the ground wire(s). A central screw tightens the washer against the ground wire(s). The result is similar to that described above with conventional screw type ground wire clamps, i.e., a relatively sharp point contact (in this case, the sharp edge or corner of the washer) engages the ground wire and likely nicks the wire to create a stress riser.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. Thus, an electrical bonding block with grounding lug solving the aforementioned problems is desired.